It is generally known that conventional primary and secondary electric cells and batteries are subject to serious limitation on their use where substantial power is required, for example, as a power source for automobiles or for the propulsion of marine craft such as submarines. Widely used lead-acid batteries of the automobile industry are sturdy and generally dependable but have power/weight ratios which are far too low for the substantial power requirements for propulsion. This is also true of zinc type batteries and other commercially available electric cells. In general, the problem is to achieve energy density (watt hrs./lb.) and power density (watts/lb.) ratios in an electric cell or battery, which will be of such order as to meet the necessary power requirements.
Significant improvements in energy and power densities can be obtained by replacing the dense, high atomic weight metals, such as lead, with the less dense, low atomic weight alkali (lithium, sodium, potassium) and alkaline earth (magnesium, calcium) metals. These active metals react rapidly with water and thus a suitable non-aqueous solvent must be used. This often leads to a moderate saving in weight in that most nonaqueous solvents are less dense than water. Electric cells based on use of these materials, theoretically at least, enable substantially higher power/weight ratios to be obtained than in the more conventional batteries. By way of illustration, a complete lithium battery should be capable of achieving current and energy density ratios of the order of ten to 20 times that obtained with the conventional lead-acid battery. However, to date, and despite the obvious benefits to be obtained, no widely successful battery or electric cell has been developed wherein the lighter active metals are utilized. In general, these active metals are so reactive, particularly in the presence of moisture or atmospheric air (including nitrogen as well as oxygen), that they not only present hazards but also require expensive equipment and handling procedures for their use. By way of illustration, known lithium sulfur dioxide batteries are not only excessively expensive to fabricate (principally because of the problems in handling the metallic lithium), but also suffer the further difficulty that they are not designed to be rechargeable.
A further particular problem commonly encountered in electric cells and batteries, is a high degree of inherent internal resistance to current flow. This internal resistance leads to overheating and consequent ineffectiveness of the battery in use, as evidenced by the well know "burn out" under conditions of severe or continued loading.
Based on the foregoing, it will be apparent that the development of an improved battery cell and system is greatly to be desired, particularly as respects present limitations on maximum energy and power density ratios obtainable in current cells, the relatively low power/weight ratios available, and the difficulties associated with handling highly reactive but potentially highly successful electrode materials.